Charles e



U. E. SURIBNER.

MULTIPLE SWITGHBOARD SYSTEM FOR TELEPHONE EXCHANGES.

Nb. 593,611. PatentedNom 16, 1897.

L Ev 11 3mm aha/7' ,sZScr' new UNITED STATES P TENT OFFICE;

CHARLES E. SCRIBNER, CIT CHICAGO, ILLINOIS, ASSIGNOR TO THE WESTERNELECTRIC COMPANY, OF SAME PLACE.

' MULHPLE-SWITCHBOARD SYSTEM FOR TELEPHONE-EXCHANGES.

SPECIFICATION forming part of Letters Patent No. 593,611, dated November16, 1897. Application filed May 13, 1892. Serial No. 432,898. (Novitae.)

To all whom it may concern;

Be it known that I, CHARLES E. SORIBNER, a citizen of the United States,residing at Chicago, in the county of Cook and State of Illinois, haveinvented a certainnew and useful- Improvement in Multiple-SwitchboardSystems for Telephone-Exchanges, (Case No. 293,) of which the followingis a full, clear,

concise, and exact description, reference being had to the accompanyingdrawing, forming a part of this specification.

My invention relates to multiple-switchboard systems in which theindividual an nunciator of a telephone-line is permanently connectedwith the line and is shunted by a clearing-out annunciator or itsequivalent re sistance in the cord-circuit when connection taken by thepermanently-closed branch, in-

cluding the annunciator, in relation to that taken by the occasionallyclosed or shunting branch when connection is established to a line, sothat the individual annunciator shall be certainly prevented fromresponding to clearing-out signals without making the permanently-closedbranch of very high resist- In a former application, Case No. 276, filedOctober 29, 1891, 1 have described such a multiple-switchboard system inwhich the individual annunciator is constructed of very high resistanceand retardation, theclearingout annunciator or shunting-annunciator inthe cord-circuit being of relatively low resistance, and in another,Case No. 282, Patent No. 483,175, issued September 27, 1892, I havedescribed a system of the same general type in which a condenser isincluded in the permanently-closed branch with the individualannunciator of such capacity as to transmit only so small a portion ofthe signaling-current as to operatethe individual annunciator when noconnection exists to line, the remainder of the current being forced totraverse the shunting-circuit after a connection ex ists. In theinvention herein I have accom plished the same general result by causingthe signaling-currents to act inductively instead of directly to operatethe individual an nunciator. The mutual induction between thepermanently-closed branch or loop of the line-circuit and the localcircuit containing the annunciator may be so determined or ad-' justedas to transmit only so much of the signaling'current as is necessary tooperate the annunciator, and, if desired,the permanently closed loop maybe constructed of'high resistanceand retardation, the localannunciator-circuit being of relatively low resistance. The size of theannunciator may thus be reduced to within moderate limits, so as not tooccupymuch space in the switchboard, the induction-coil or equivalent inthe permanently-closed loop being disposed in some convenient localityoutside of the switchboard.

In my invention I provide an induction or repeating coil having one ofits windings included in the permanently-closed loop of the line and theother in a permanently-closed local circuit with the individualannunciator of the same line. A clearing-out annunciator or retardationcoil is placed in a bridge connection between the different sides of thecord-circuit used in establishing connection with the line. The relativeresistances of the permanently-closed loop and the clearing-outannunciator in the cord-circuit may be so adjusted that thepermanently-closed loop will be shunted to a considerable extent whenthe cord-circuit is connected to the line andthe inductive relation ofthe two windings of the repeating-coil in the line-circuit may be soarranged as to the number of windings, their size, and the magneticconductivity of their magnetic circuit that the local circuit con- 0'taining the annunciator shall receive sufficient current to operate itsatisfactorily whenthe line is unconnected, but shall receiveinsufficient current to operate it under. any circumstances when theline is connected or 5 shunted. A feature and peculiar advantage of myinvention consists in the fact that leak or stray currents findingcircuit through the line, such as shunted portions of the current 'ment.

of grounded electric-railway systems, do not affect the annuneiator inmy invention, since such steady currents are not repeated into theannunciator-circuit. Similarly a much heavier test-battery may beemployed thanheretofore, because whatever current from the test-batteryfinds circuit through the induction-coil in a grounded line does notaffect the annunciator. A test-battery which will give a much moresatisfactory test than has been possible heretofore may thus be employedin connection with my invention.

My invention is illustrated in the accompanyin g drawing. Thereinlhaveshown two telephone-substations connected by line-circuit, which aremetallic and grounded circuits, respectively, with their particularspring jacks and individual annunciators upon two sections of multipleswitchboard, the two lines being connected together by means ofloop-plugs and a cord-circuit of the usual construction upon one of theboards. An additional plug-and-cord circuit is shown at the other board,one of its plugs being shown in the position of testing a line todetermine whether it is already in use or not.

The apparatus at the substation-for example, substation 1-is of theusual character. It consists briefly of a calling-generator a andsignal-bell a and a telephone-transmitter a and receiver a connected indifferent branches from one side I) of the line, and a gravity-switch a,connected to the other side I) of the line, adapted to connect thetelephone apparatus or the signaling apparatus alternately into theline-circuit, according to the position of the switch-lever. The linesI) I) extend to the telephone-exchange, where they are connected tospring-jack switches c and 0 upon two sections of multiple switchboard dand cl, respectively. The springjacks are of well-known construction.Each consists of a line-spring e and a test-ring e, which are connectedto the different sides I) and b of the line-circuit, respectively. Theline circuit is continued at the exchange through a permanently-closedloop, including one windingf of the repeating-coilf. The other winding fof the repeating-coil is included in a local circuit with the winding orcoil of the individual annunciator g, of wellkno-wn construction,situated upon theboard cl near the jack 0 of its line. The apparatusconnected with substation 2 is of similar construction and arrangement,the individual annunciator 9', however, being placed upon the othersection (Z of switchboard near its jack 0 so as to be under the care ofanother attendant operator. The line-circuit of this station is shown asgrounded, the conductor 5 being continued through earth anda resistanceinstead of being a continuous metallic conductor. The cord-circuits orcon nectin g appliances are of well-known-arra'nge- Two-loop-plugs h hareprovidecheach having two contact-points, a tip 2', and sleeve z",adapted to make contact with the linespring a and the test-ring 6,respectively, of the jack, into which the plug may be inserted. Likecontact-pieces of the two plugs are connected together throughconductors k k. Two calling-keys H are included in the circuit joiningthe two plugs, each arranged to disconnect both contact-pieces of one ofthe plugs from those of the other and to connect them to the twoterminals m m of the calling-generator 01, whereby the generator a maybe looped into any line-circuit to send a call to the substation.

A listening-key 0 is provided in connection with each cord-circuit,adapted to connect an operators telephone set 1) in a cross-wire orbridge between the different conductors 7c 7r, joining the plugs. Agrounded battery q is connected to the sleeve-strand k of eachcordcircuit to create a difference of potential between the test-rings eof a line, into which any plug may be inserted, and the earth and aground connection is extended from the middle of the operatorstelephone-receiver p to earth in order that an existence of the difference of potential between the test-rings of the connected line andearth may be determined by applying one of the loop-plugs to thetest-ring in the ordinary manner. A clearing-out annunciator '1 isincluded in another cross-wire or bridge connection between theconductors 7t Suppose that subscriber at station 1 desires tocommunicate with another subscriber of the exchange system-for example,at station 2. His telephone-switch a being in its lowest position, herotates the calling-generator a, thus sending current over lines I) b tothe exchange, where it finds circuit through the coil f of therepeating-coil f. The alternating or pulsating current flowing in thiscoil produces a corresponding current in the coil f 2 of therepeating-coil, thereby energizing the electromagnet of annunciator gand operating the annuneiator. .The attention of the operator at board dbeing thus attracted to the line to station 1, the operator inserts theplug h into the jack 0' of that line at her board and depresses theplunger of listeningkey 0, thus connecting her telephone set 1) in aloop with the line-circuit to substation 1. Having received the orderfrom. subscriber at substation 1, the operator proceeds to test thespring-jack c of line to station 2 at her board (1 to determine whetherthe line is already in use or not by applying the tip of her loopplug hto the test-ring of the spring-jack in the well-known manner. If theline were in use, the test-ring would possess a diiference of potentialfrom the earth on account of a battery q being connected to it, andcurrent would flow from the test-ring, tested through one side 7c of thecord-circuit, to the testing operators telephone-receiver p and thenceto earth, causing a click in the telephone, whereby the operator-wouldbe apprised that the line was already in use. Ilaving found the line tobeidl'e, the operator at board din- I sponding'contact-pieces of plug h,thence line-circuit.

. switch-hook on, again turns the generator a, 20

small portion of the calling-current will find 593,611 g g s serts theplug 71. into the jack 0 and depresses the plunger of her calling-key Z,sending a calling-signal to station 2. When the subscriber at station 2has removed his telephone from the switch-hook (1 the two subscribersare in communication over a circuit which may be traced over lines I) bto the contactpieces of spring-jack c, thence to the correthrough thecord-circuit to the similar contact-pieces of plug h to theline-contacts of spring-jack c thence over lines b b to substation 2.The telephone set 19 of operator at board d remains'in a bridgeconnection between the two sides of this loop-circuit.

When the subscribers have finished their conversation, one of them, saythat one at station 1, replacing his telephone upon the sending a signalto the exchange for disconnection. The larger part of this current findscircuit through the plug it to the cord-circuit k, thence through thelow-resistance clearing-out annunciator'r, thus operating thatannunciator and indicating the disconnection-signal to the operator atboard d. A

circuit through the high-resistance coil f of repeating-coil f and willinduce a slight cur-, rent in the local circuit containing theannunciator g; but this current will be wholly insufficient to operatethe annunciator. Another inconsiderable portion of the signalingcurrentwill escape through the-cord-circuit to the lines 5 b thence through therepeating-coil f of that line, but the'annunciator g will remainsimilarly unresponsive.

The coils f of the repeating-coils fmay be readily constructed of veryhigh retardation, so as to shunt an inappreciable portion of thetelephonic current. Much higher self-induction may be attained in therepeating-coil than would be possible in the annunciator g within areasonable space.

The clearing-out annunciator r is preferably of high retardation, so asnot to interfere with telephonic transmission. This coil 1' may bereplaced, if desired, by a retarda tion-coil or resistance-coil withoutdeparting from the spirit of my invention, since its particular functiontherein is to shunt the coil f of the repeating-coil f when connected tothe Having thus described my invention, I claim as new and desire tosecure by Letters Patent- 1. The combination with a telephone-line andspring-jacks connected therewith in a' switchboard, a repeatingcoil anda line-annunciator, a bridge of the line-circuit including one helix ofthe repeating-coil, and a local circuit. including the other helix ofthe I repeating-coil and the line-annunciator, sub

stantially as described.

2. The combination with a telephone-line circuit of a repeating-coil,one of Whose coils is included permanently inthe line-circuit and theother of whose coils is included in a local'circuit with an individualannunciator, and means for-shunting the first-mentioned coil of therepeating-coil when connection is established with the line,substantially as described.

3. The combination with a telephone-line extending-from a substationto'an exchange of spring-jack switches at the exchange each having twocontact-pieces connected to the different sides of the line-circuitrespectively, a repeating-coil having one of its windings included in apermanently-closed loop of the line-circuit, an individual annunciator.included in a local circuit with the remaining coil of saidrepeating-coil, a loop-plug adapted for insertion into any one of thespring-jacks, and a retardation-coil in a branch between the differentcontact-pieces of the loop-plug, the resistance of thepermanently-closed loop of the line-circuit containing the winding ofthe repeating-coil, and the resistance of said retardation-coil being soadjusted with relation to each other as to cause current insuffi-.

cient to operate said annunciator to flow "in said local circuit when acall-signal is sent in the line-circuit, when the loop-plug is insertedin a spring-jack of the line, substantially as describer 4. Thecombination with a line-circuit extending from a substation to anexchange, spring-jacks at the exchange, a repeatingcoil having twohelices one included in a per-- manently-closed loop of theline-circuit, and the other included in a local circuit with anindividual annunciator, a loop-plugadapted for insertion into anyspring-jack, a resist ance in circuit between the differentcontactpieces of the loop-plug, the resistance of the helix of therepeating-coil included in the line-circuit being so adjusted withrelation to the resistance included in circuit between thecontact-pieces of the loop-plug, and the mutual induction between thetwo helices of the repeating-coil being so adjusted that alternatingcurrent call-signals sent upon the unconnected line-circuit shalloperate said annunciator, but that such current shall fail to operatesaid annunciator when said repeatin g-coil is shunted by the resistance,substantially as described. a

In witness whereof I hereunto subscribe my name this 10th day of March,A. D. 1892.

- CHARLES E. SORIBNER. Witnesses:

M. J. TALLETT, v Gnonen W. MOMAHON.

